Sound-absorbing material for walls and ceilings



Sept. 15, 1925.

v W. S. TRADER SOUND ABSORBING MATERIAL FOR WALLS AND GEILINGS forigiml'FiLled sept. 5, 1922 Patented Sept. i5, 1925.

* Ni'rED sTAri-:s PATEN'ioFFicE.

W'ILBUR SEWALL TRADER, OF ST.l LOUIS,

Missoula,

ASSIGNOR, BY MESNE ASSIGN- MENTS, T "DAHLBERG @c COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

To all wlw/m, t may concern.: v Be it known that I, WILBR SEWALL TRADER, a citizen of the United States, re-

siding in the city of St. Louis and State of i Missouri, have invented new and useful lm# provements in Sound-Absorbing Materials for Walls and Ceilings, of which the" following is a specification.

This invention relates to the art of iinl0 proving the acoustical properties of auditoriums, oilice rooms and the like, and 1s especially concerned with certain new and usefulimprovements in the structure of sound absorbing material now very generally used for this purpose. This sound absorbing material is usually inthe form of blocks or sheets of especially prepared material characterized by extreme porosity and is usually vapproximately one inch in thickness.`

It is the object of-this invention to provide a structural and facing material for surfacing walls and ceilings in auditoriums, ofces and the like, which shall correct acoustical diiiculties of all kinds by the prevention of excessive reverberations and echo, the injurious focusing of sound, and the accumulation of noise and sounds of all kinds in such enclosed spaces.

With this general object in view, the invention resides essentially in providingthe block, mat,`sheet, or other form of sound absorbing material, with means for increasing the penetrability or absorption of the sound Waves by the material or, in other words, to increase the ability of the material to pocket and destroy sound Waves pro- 'ected against it land which would otherwise reflected from the surface of the material and produce the characteristic phenomena of reverberation and echo, or incases of eX- cessive conflict between sound waves projected vfrom different parts of the auditoriun'iv or thelike, rendering it diiiicult for articulate speech to be heard in certain portions of the auditorium. i

This object is attained by providing the sound absorbing material with a greater or "less number of holes, perforations, recesses', indentations, pockets, grooves or the like, which may be of such form, configuration, and -depth as circumstances tobe desirable, andA any' one or more of which modification of the, surface of the may indicate v SOUND-ABSORBING MA'IEBAL FOR WALLS AND CEILINGS.

Application filed September 5, 1922, Serial No. 586,112. Renewed .Tilly 18, 1925.

'sound absorbing material may be combinedt in a given area thereof. By this means, the eliciency of the sound absorbing inaterial in the percentage of the sound waves absorbed, is greatly increased and'there is also produced a more uniform percentage of the absorption of sound waves lying betweef the pitch values of C1 and C7 inclusive. By this means, the scientifically demonstrated limitations of sound absorbing materials, heretofore employed, are overcome and it is rendered possible to overcomeacoustical defects and to decrease undesirable sound manifestations in an auditorium or other enclosedfspace to an extent which it is impossible to attain `with the types of sound absorbingy material hereto-A fore employed. The limitations of such materia have been recognized and stated by one of the leading authorities inthis eld. The late Wallace C. Sabine, former professor of physics of Harvard University, in the specification of Patent No. 1,197,956,

.(Sabine & Guastavino) dated September 1,2,

1916, page 1, lines 103. to 109, inclusive, ref ferring to a type of sound absorbingmaterial which he and his co-patentee had invented, sets forth such limitations in the following language.

The ower of our product to absorb sounds of3 different pitches is dependent to a very large extent upon the dimensions of thepores between the particles f which it isv composed, and the dimensions of these pores are largely dependent upon the dimensions of the particles.

'And, at page 2, lines 23 to 80 inclusive, of the same patent, he further states:

Carefully conducted scientific tests have also shown that our finished product manufactured according to our process above described, will absorb much in excess of"1li%\ of sounds lying in the pitch between the middle C and the C, which are the characteristic sounds which distinguish articulate speech?? The limitations of the highest type of sound absorbing material thus referred to, and the relatively low percentage of absorption of sound waves lying between certain rlimits of pitch, results from the fact that structural material prepared as describedL by these? patentees does not oi'er third octave above middle l ioo sufficiently large or extensive pockets, openings, or cavities in the surface of the material exposed to the sound waves to trap, as it were, the sound waves and destroy their formation and thus prevent their reflection by the wall or ceiling.

By the provision of suitable apertures, cavities, recesses or the like, in the surface of the material exposed to the sound waves, and into which they are projected leither directly or indirectly, I secure the result that the entering waves will be pocketed or smoothered and thus eliminated, due to the fact that the sound waves striking the surface of the wall or ceiling covered with sound absorbing material prepared according to my invention, are almost entirely isolated or confined within such recesses or cavities, and to the further fact that the provision of these cavities, recesses or the like which can be entered by the sound waves, provide a much larger area of sound absorbing surface than the material heretofore employed, which is characterized by its cellular or porous structure. I have found that sound absorbing material provided with holes, cavities or the like, according to my invention, will absorb and eliminate at a practically uniform percentage, all sounds lying in the pitch between C1 and C7, and to function in this manner, it is not necessary to graduate and regulate the size of the pores in the sound absorbing material in relation to the ability of these pores to absorb sounds of all or different pitch values. Carefully conducted tests have shown that sound absorbing material of a uniform thickness of one inch which will absorb 30% of sound lying in the pitch of middle C and oneoctave above, will absorb much in excess of 50% of sound lying in the pitch between C1 and C7 inclusive, by incorporating through the thickness of this sound absorbing material round holes or perforations -156 of an inch in diameter and spaced of an inch' apart from edge to e Ue.

'Ihis invention differs from the invention of my co-pending application Serial No. 742,777, led October 10, 1924, entitled Sound absorbing board for walls and ceilings, in that, this invention is not limited to the fibrous materials made the subject matter of said co-pending application, but includes all materials to which it may be desired to apply the principles and perforations of this invention. n

In order that my invention will be better understood, I have illustrated the same with yvarious forms or embodiments thereof in the accompanying drawing in which- Figure 1 is a vertical sectional view through a portion of a block of sound absorbing material, showing the preferred embodiment of the invention comprising a series of round holes extending through the material from its inner to its outer surface;

Figure 2 is a broken plan View of the same;

Figure 3 is a view similar to Figure 1 but illustrating a modification in the provision of a sheet of porous material covering the inner or exposed surface of the block;

Figure 4 is a broken plan view illustrating the construction of Figure 3, a part of the material further broken away to show the application of the porous covering;

Figures 5, 7 ,'8 and 9 are views similar to Figure 1 illustrating further modified constructions; and

Figure 6 is a broken bottom plan view o a block of sound absorbing material showing a still further modification.

Referring now to the drawing, the numeral 1 indicates a block of sound absorbing material of any usual or preferred composition, said block being usually about one inch in thickness. )Extending through this block from its inner or exposed face `to its rear side, are a series of apertures 2 which in practice I have made T5, of an inch in diameter and spaced approximately W8 of an inch apart from edge to edge. The arrows at the bottom of this figure and in other figures, indicate the surface exposed to the sound waves.

I have found that itis not in all cases necessary that the open ends of the apertures, cavities, or the like, be exposed directly to the sound waves, but for artistic effects, or for the purpose of ornamentation, the inner or exposed surface of the sound absorbing block may be covered with a thin sheet of porous material and such a sheet I have illustrated in Figure 3 as applied to the construction of the block in Figure 1, the sheet being indicated by the numeral 3.

It may be `here stated that a porous sheet or layer such as indicated at 3, Figure 3, may also be applied to the exposed surface in any of the other forms or modifications illustrated in other views of the drawing.`

Such a sheet does not materially interfere with the entrance of the sound waves into thke interior of the apertures, cavities or the li e.

In Figure 5 I have illustrated a modified construction in which the block or slab 1 is provided with openings or recesses 4, preferably circular, extending about half way through the material from the exposed surface.

Figure 6 illustrates a further modification in which the recesses or the like are made in the form of continuous slots 5 of greater or less depth, provided on the outer or exposed surface of 'the slab and extending from edge to edge thereof either transversely, longitudinally, diagonally, 01,' @then wise.

, the openings extending ,through 1,554,179 sli;

in Figure 7 is illustrated a Suu further modification in Figure l, but in which the -apertures 6 are cone-shaped, the larger end of the opening being at the exposed surface of the slab.

In Figure 8 a still further modiiication is shown in which the block or slab is provided with recesses or openings 7 of conical formation extending into the block from the ex- Dosed surface thereof to a distance of about one-half its thickness.

Finally, modification in Figure 9 in which interdental recesses or apertures 8 are provided, the slab from front to rear thereof, but the portions of the openings, extending about one-half through the thickness of the slab, being enlarged as indicated at 9, the remaining part of each aperture or opening being of about the size of the apertures 2 of Figure l, as illustrated at 10.

As will be readily understood, the purpose of enlarging the area of the recesses, openings, apertures orthe like, at the exposed face of the slab, as illustrated in Figcular apertures can readily drilling, boring, or the` like.

ures 7, 8 and 9, is for the purpose of increasing the permeability of the slab by the sound waves and also sound absorbing area which, of course, results fromv increasing the .interior surface of the apertures, openings, or the like, exposed to the sound waves.

It is immaterial, so far asy the main purpose of my invention is concerned, how the various forms of apertures, recesses, or the like are formed. In the case ofthe construction shown in Figures 1 and 3, the cirbe provided by In other forms, the recesses or other character of openings I have illustrated a still further' for increasing the could be made by molding them into the slab or block when the latter is formed.

What I claim is 1. A sound deadening construction comprising a layer of material which has sound absorbing characteristics, and having therein independent artificial openings extending inwardly from a surface of said material, whereby sound waves reaching said surface will be absorbed.

2. A sound deadening construction comprising a layer of materlal which has sound absorbing characteristics, and having there- 'in independent artificial ing inwardly from the exposed surface of said materiahsaid openings being of a relatively decreasing dlameter inwardly from the exposed surface, 'whereby sound waves reaching said surface will be absorbed.

3. A sound absorbing construction comprising a layer of material having sound absorbing qualities provided with independent perforations of substantially fiveeighths of an inch in diameter extending inwardly from a surface of said material, whereby sound waves lyin in the pitch between the notes C1 and 57 of the musical scale will be absorbed. y

4. A sound absorbing construction comprising a layer of material having sound absorbing qualities provided with independent perforations of substantially fiveeighths of an inch in diameter and spaced substantially three-eighths of an inch apart from edge to edge, said perforations extending inwardly from a surface of said maopenings extendterial, whereby sound waves lying in the pitch between the notes C1 and C7 of the musical scale will be absorbed.

In testimony whereof, I have hereunto set my hand. v

WILBUR TRADER.

DISCLAIMER 1,554,179.Wtzbwsmall Trader, st. Louis, M0. SOUND-BSO ALLs AND CEILINGs. filed October 27, 1936, by

from which the said openings extend inwardly,

are of such size and number that the interior surfaces thereof tenally increase the sound absorption of said material,

November 17, 1986.]

[Qctal Gazette Patent dated September 15, 1925.

the assignee,

Hereby disclaims from the Vscope of claims 1 and 3 0f said Letters Patent all RBING MATERIAL FoR Disclaimer The Oelote Corporation.

is sound absorbing and said openings are meffective to ma- 

